Pace 2500B gradually and intermittently lost all but BBC channels. CNN went first, Classic FM one of the last. Signal good also quality. Lost channels report no signal even though signal strength shows max. Replaced LNB and cable no change. Substituted an old Pace box, all comes good. Suspect loss of 22kHz but this shouldn't affect CNN? Have full anti-static surface mount replacement capability, suspect resistor gradually going high then open, or capacitor deteriorating. Is 22kHz generated in ZIF module if not whereabouts on the main PCB. Can't so far get hold of the service manual.